1. Field of the Invention
The present invention relates to a developer depositing unit for an image forming apparatus for electrostatically depositing a charged developer on a support member such as an ordinary sheet of paper.
2. Description of the Related Art
There has been conventionally put into practical use a color copying machine, for example, where a microcapsule sheet, exposed to light, is then superposed on a developing sheet and subjected to a pressure-developing process, thus forming the copied image on the developing sheet. The developing sheets used, that is those on the market, have been coated with a developer for specific use in a color copying machine. However, the requirement to use specialized developing sheets, that may be specific to the microcapsule sheet, cause stockage problems both in terms of timely availability and space for storage. To address this problem, a developer depositing unit capable of easily manufacturing the developing sheet using of an ordinary sheet of paper is disclosed, for example, in Japanese Patent Application No. 63-170660 (now Japanese Utility Model Laid-Open Publication No. 2-90840) by the same inventor as the present invention.
In such a unit, a carrier roller for carrying charged particles of developer is positioned in non-contacting face-to-face relationship with a support member, such as an ordinary sheet of paper, so that the developer is deposited on the support member by static electricity produced in an electric field. In another unit of this type which improves on the amount of charged developer deposited on the ordinary sheet, a frictional charge on a carrier roller and a supply roller is used. Moreover, there is also a unit having a supply roller and a carrier roller which has grooves, for the purpose of carrying an increased amount of developer for deposit on the ordinary sheet, disclosed in U.S. patent application Ser. No. 496,304, assigned to the same assignee as the present invention. The referenced patent application also discloses a second blade for removing clogged developer from and for grounding the developer carrying roller. However, the second blade does neither task effectively.
As indicated, in the developer depositing units described above, there are problems caused by the build-up of a charge on either the carrier roller or the supply roller, or both, such that the amount of developer that may be transferred to the ordinary sheet decreases over time. Further, the amount of transferable developer carried may be reduced due to the clogging of the carrier roller or the supply roller by packed, dense developer. As a result, the amount of developer deposited on the ordinary sheet support member is reduced. It is these problems that are addressed and solved by the invention as the previously described solution has proven to be ineffective.